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1,2 and 1,6 Additions of Lithium Reagents to γ‐Methylenepyran Fischer‐Type Carbene Complexes; Evolution of the 1,2 and 1,6 Adducts to Unsaturated Carbene Complexes Indirectly Stabilized by a Heteroatom, and to Pyranylidene Carbene Complexes
Author(s) -
Caro Bertrand,
Le Poul Pascal,
RobinLe Guen Françoise,
SénéchalTocquer MarieClaude,
Saillard JeanYves,
Kahlal Samia,
Ouahab Lahcène,
Golhen Stéphane
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(200002)2000:4<577::aid-ejoc577>3.0.co;2-2
Subject(s) - carbene , chemistry , adduct , reagent , lithium (medication) , transition metal carbene complex , heteroatom , medicinal chemistry , organic chemistry , ring (chemistry) , catalysis , medicine , endocrinology
1,2 and 1,6 additions of lithium reagents to γ‐methylenepyran Fischer‐type carbene complexes are described. The 1,2 adducts obtained from alkynyllithium addition evolve by a 1,3 shift of the W(CO) 5 fragment to give allenyltungsten carbonyl intermediates. Reaction with degassed water affords unsaturated carbene complexes indirectly stabilized by a heteroatom. The 1,6 anionic addition products are quenched by H 2 O at low temperature to give α,δ‐unsaturated carbene complexes. On warming, an evolution occurs leading to new pyranylidene carbene complexes.